Facebook is now the leading source of traffic for news, overtaking search giant Google, according to traffic analytics firm Parse.ly.

Parse.ly reports that from May to July, social media sources, of which Facebook is the biggest, accounted for 43% of the traffic to its network of media sites. That's bigger compared to Google's 38%, and more than twice as much as Facebook's record in January last year.

Parse.ly counts traditional publishers like Wired, The Atlantic, Reuters, and The Daily Telegraph among its more than 400 clients. Also part of its network are digital-only outlets Mashable, The Next Web, and Business Insider. In a month, the network records some six billion page views and more than one billion unique visitors.

This is not the first time Facebook has surpassed Google in terms of news referrals. Last October, it took the top spot although only by a small margin.

Andrew Montalenti, Parse.ly's chief technical officer, says all this happened after Facebook began collaborating with publishers to curate and promote content. "I believe the reason Facebook did this is because they realized that a lot of the interesting conversations happening around the web were happening around major news, media, and information."

A few days ago, it was reported that Facebook appeared to be developing a stand-alone news app that looks like Twitter. Business Insider has obtained screenshots of the new product, which is purportedly part of the social network's Facebook for Business initiative.

Another traffic analytics firm, Chartbeat, has also noted Facebook's rise as a traffic source for news. "When we look at all the sites over our network, a third have more Facebook traffic than Google," Tony Haile, chief executive of Chartbeat, told Fortune. "But when we only look at the largest 20%, about half of them have more traffic from Facebook than Google."

It's not clear what caused Google's decline as a top traffic source. But Montalenti says it could be due to a change in the search giant's referral practices. Previously, publishers knew what keywords to use in directing traffic to their sites because Google provided the data. But now no such information is available. Even Facebook does not tell how it's algorithm functions.

Montalenti says this lack of transparency has made it difficult for publishers to come up with an effective strategy to promote their content on social media.